The term “sound velocity” is a recognized shorthand expression describing a characteristic of the speed at which sound waves travel in a medium. The speed of sound varies depending on the medium through which the sound waves pass. It usually is a parameter used in describing properties of different substances or mediums. Knowing the value of the sound velocity of a particular medium, such as a flowing fluid, liquid or gas, permits many different characteristics or properties of the fluid to be determined. Using the sound velocity together with appropriate mathematical relationships allows for determination of various characteristics or properties of the medium such as its density, purity concentration, components of the medium composition, etc.
Several different types of apparatus exist for measuring the sound velocity in a fluid flowing in flexible or rigid tubing. The term “tubing” is used hereafter to define both the flexible, semi-rigid, and rigid type. Flexible tubing is of a material, such as an elastomeric, that can be deformed. Rigid tubing can be of any material such as plastic or metal and is not normally deformable. Semi-rigid tubing can be of a material other that an elastomeric that can be somewhat deformed.
Apparatus for measuring sound velocity is generally of either the contact or non-invasive type. In the contact type, some part or parts of the measuring apparatus come into direct contact with the fluid. In the non-invasive type, the sound velocity is measured without any part of the measuring apparatus coming into contact with the fluid. Whatever apparatus is used for measuring the sound velocity, it is desired that it be as simple in construction and operation as possible and that it does not adversely hinder or affect the application or other apparatus with which it is being used.